A technical problem addressed by the present technological advancement is transforming a discontinuous, i.e. faulted, subsurface reservoir into a continuous, fault-free space where a complete geological model based on the geological concepts of interest can be built and updated efficiently. However, it should be noted that the present technological advancement is not a technique for reverse engineering of faulting events, a process known as fault restoration in structural geology. However, the terms “fault removal” and “fault restoration” are sometimes used interchangeably in the literature.
Faults break up depositional strata by cutting across and offsetting them. As such, the preserved geometry of a subsurface reservoir can be significantly different from its geometry at the time active sedimentation subsided. As geological concepts are often tied to distinct geological events and/or environments of deposition, it can be quite difficult and cumbersome to apply them to fragmented and offset regions. Moreover, incorporation of new data into such a geologic model, or changing the geological interpretation or structural framework, are not necessarily straightforward tasks and may require building the geological model from “scratch” in its entirety. Therefore, it is desirable to transform discontinuous faulted regions into continuous regions where geological concepts can be easily applied and modified. This is a main focus of the present technological advancement.
Fault removal has received some attention the in the last decade and at least two patents exist on this topic.
In U.S. Pat. No. 7,480,205, incorporated herein by reference in its entirety, the inventor addresses the problem of seismic fault restoration by devising a model based on elasticity theory and using finite element and boundary element numerical methods for validating the correlations of interpreted horizons. The method is claimed to be computationally fast enough to allow interactive fault reversal and permit experimentation with various unfaulting scenarios so that a geologically acceptable solution is achieved. This patent has the following short comings
First, it fails to address the quality of the mapping between the two spaces. It is well known by someone skilled in the technical field that the distortion in the vicinity of faults for this class of problems can lead to significant distortion or overturning of internal surfaces and/or layering. Second, the described approach treats faults on a one-by-one basis, in no particular order, and is more suitable for validating the seismic interpretation while the present technological advancement deals with sequential fault removal in the reverse chronological order.
In U.S. Patent application publication 2011/0106507, incorporated herein by reference in its entirety, the authors use a similar solid material deformation model as in U.S. Pat. No. 7,480,205 and calculate fields of displacement to build a virtual deposition space matching the environment at the time of deposition.